Mechanism of Effect of Vagotomy on Pancreatic Secretion. The effect of atropine and vagotomy on secretory response to secretin and HCl will be determined. The results should indicate if there is cholinergic dependence of the effect of secretin on the pancreas and if HCl in the intestine stimulates pancreatic secretion in part by a cholinergic reflex. Trophic Effects of Gastrointestinal Hormones. Pancreatic weight, DNA synthesis and content, and enzyme content will be measured after treatment with VIP, glucagon, and bombesin. Structure-Activity Relations of Cholecystokinin and Gastrin. The potency of gastrin and CCK-related peptides for gastric acid and pancreatic protein secretion will be determined in rats. The minimal peptide chain length which confers selectivity of effect will be determined by comparing these potency ratios.